How to Use Pool Shock to Purify Water

Jodie Weston Jodie Weston  |  Updated: October 20, 2020
How to Use Pool Shock to Purify Water

If I were to ask how many of you store liquid bleach along with your other prepping supplies, I am certain that a good percentage of you would raise your hands. Liquid bleach is a powerful disinfectant and sanitizer but did you know that there is something better? Something with an almost indefinite shelf life that is inexpensive and takes almost no room to store?

That something is the chemical Calcium Hypochlorite most commonly known as Pool Shock.

How to Use Pool Shock to Purify Water - Backdoor Survival

I have known about Pool Shock for years but because it is not readily available in my area, I never took the time to search it out so I could stockpile some for my own emergency preps. That has now changed and today I plan to show you how to use Pool Shock the easy way, step by step.

Why Not Bleach?

Before we start, you may be asking “why not use liquid chlorine bleach?”. There are a few problems with liquid household bleach. It takes a lot of room to store bleach plus the usable shelf life is only six months to a year depending on storage conditions.

The folks at Clorox say this:

The active ingredient in liquid bleach, sodium hypochlorite, is very sensitive to high heat and freezing, but under normal home storage conditions, it should still perform well for nine to twelve months.

In addition to limited shelf life, there is another problem. I have had reports from Backdoor Survival readers telling me that in their area, they can only purchase “Clorox Ultra” which is concentrated. When I called Clorox to ask how to use concentrated bleach to purify water, they said that it was not intended to be used in that manner and why would I want to do that anyway. Seriously, their representative actually said that.

Pool Shock – The Boilerplate

When I started doing research for this article, I visited some of the most respected survival and preparedness blogs and forums for background material. After all, pool shock is pool shock and there must be some standards for use, right?

With just one exception, all of the sites I visited included this boilerplate from the EPA:

You can use granular calcium hypochlorite to disinfect water.

Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately ¼ ounce) for each two gallons of water, or 5 milliliters (approximately 7 grams) per 7.5 liters of water.

The mixture will produce a stock chlorine solution of approximately 500 milligrams per liter, since the calcium hypochlorite has available chlorine equal to 70 percent of its weight.

To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of stock chlorine to each 12.5 gallons of water or (approximately ½ liter to 50 liters of water) to be disinfected.

To remove any objectionable chlorine odor, aerate the disinfected water by pouring it back and forth from one clean container to another.

Have your eyes glazed over yet? Mine have. Being an accountant, I like to deal in absolutes so what is this business about “one heaping teaspoon”? Plus, what’s up with the references to “approximately” and “roughly”?

I decided that it was time to do my own testing, and sure enough, each time I measured out a heaping teaspoon, I had different results; they ran the gamut from 1 1/4 teaspoons to 2 teaspoons. This made my head hurt.

Another thing. Over and over I read that you should use pool shock that is a minimum of 78% calcium hypochlorite with the balance being inert ingredients. Fair enough, but there are two problems with this. First, what you find locally maybe 68%, it may be 78%, or it may be something else. Second, the EPA makes no such recommendation or at least none that I could find. They simply say “high-test”.

Did I mention this made my head hurt?

But there is more. I actually found a couple of sites that said to use one heaping tablespoon of Pool Shock for every two gallons of water! You know, just because you find something on the internet does not mean it is true.

My conclusion? The exact amount and the exact percentage does not matter as long as it is within a reasonable range and close to the EPA standard. I do think it is important that the pool shock does not contain other additives that may or may not be safe even when highly diluted. Other than that, however, it is my belief that the precise percentage of Calcium Hypochlorite to inert ingredients does not matter as long as it is 68% or higher.

For my own use, I settled on 1 teaspoon of pool shock per gallon of water when making up my stock chlorine solution. Then, to disinfect water, I used 3/4 ounce of my pool shock solution to treat a gallon of water. This makes it easy to calculate how much to use for water disinfection, regardless of the size of your container.

Step-by-Step: How to Purify Water Using Pool Shock

The first thing I did was to gather my supplies. Notice that I used eye protection goggles and rubber gloves. Other supplies included an empty bleach bottle, funnel, shot glass, and measuring spoons.

How to Use Pool Shock to Purify Water - Backdoor Survival

I verified the size of my stock chlorine solution container, namely a repurposed bleach bottle. My bottle held 1.42 gallons and I wrote this on the outside with a Sharpie pen. My intent, however, was to only prepare 1 gallon of stock solution to keep the math simple.

How to Use Pool Shock to Purify Water - Backdoor Survival

After donning my protection gear, I added water to my stock solution bottle, carefully measuring the quantity. I used exactly one gallon of water.

How to Use Pool Shock to Purify Water - Backdoor Survival

I then measured out some pool shock; one level teaspoon to be exact. I put the cap back on the bottle and swished it around a bit. I gave it a sniff test and it definitely smelled bleach-like.

How to Use Pool Shock to Purify Water - Backdoor Survival

The next step was to purify water. I wanted to make drinking water and for me, the smaller the jug the better. I chose a 64 ounce repurposed apple juice jug. Remember the easy math? The EPA says 1 part chlorine solution to 100 parts water so the math is 64/100 = .64 ounces.

Keeping things easy, that translates into approximately 2/3rd ounce. Remember, the EPA guideline uses the word “approximately” all over the place. That was good enough for me. To easily measure the proper dilution, I used a mini shot glass that had measurement markings along the side.

How to Use Pool Shock to Purify Water - Backdoor Survival

Be sure to pour your pool shock into your water and not the other way around. The last thing you want is to splash the solution on yourself on the surrounding surfaces (although you have probably noticed that I did this outdoors).

After preparing my newly purified drinking water, I drank up. Three things. I did not throw up, I did not get diarrhea and I did not get sick or die.

I am comfortable with the results even though the solution I made may have been slightly stronger than the EPA guidelines. Then again, given the vagueness of the EPA guidelines, perhaps my measurements were spot on.

How to Use Pool Shock to Purify Water - Backdoor Survival

Note: I did not find that my water had an objectionable smell or taste. True, it was not sweet tasting like the water coming out of my Royal Berkey but it was palatable. If your own purified water has an unpleasant odor, simply aerate it by pouring it back and forth between clean containers. This trick applies to any water, not just water treated with pool shock.

How to Use Pool Shock to Purify Water - Backdoor Survival

Label your pool shock solution. This is powerful stuff. Get out your Sharpie and label the jug with as much information as you can. Store it, in the same manner, you store liquid bleach, up high and away from pets and children and in a location that is cool, dark and dry.

Also, store your unused pool shock safely. Because it is corrosive, I chose a mason jar with a plastic lid. Plus, rather than empty the pool shock into the jar, I sealed the plastic bag it came in with a clip and stuffed the bag inside of the jar.

Other Handling and Storage Considerations

I contacted the manufacturer of the pool shock I purchased and requested a Material Safety Data Sheet on the product. They promptly responded and here is what it said about handling and storage:

Keep product tightly sealed in original containers. Store product in a cool, dry, well-ventilated area. Store away from combustible or flammable products. Keep product packaging clean and free of all contamination, including, e.g. other pool treatment products, acids, organic materials, nitrogen-containing compounds, dry powder fire extinguishers (containing mono-ammonium phosphate), oxidizers, all corrosive liquids, flammable or combustible materials, etc.

Do not store product where the average daily temperature exceeds 95° F. Storage above this temperature may result in rapid decomposition, evolution of chlorine gas and heat sufficient to ignite combustible products.


Now that I have been through the process and understand the math, I am comfortable using pool shock to purify water for drinking, hygiene, and sanitation purposes. It is not, however, an excuse for not storing water nor an excuse for not having a supply of traditional water purification liquids or tabs that are pre-measured and simple to carry with you in bug-out-bags and emergency kits.

As far as I am concerned, the pool shock I have purchased is reserved for dire emergency use, period. Yes, I feel it is safe, but it is still a powerful chemical solution as is liquid bleach. I will use it as the water purification method of last resort and if the time comes, I will be thankful I have it on hand.


I have to say this: I am not a chemist and I am not an expert. My methods are my own and they work for me. That being said, if you have any hesitation at all, visit other resources including the EPA and make the decision to use pool shock your own and not just something someone told you to do. Here is a link: Emergency Disinfection of Drinking Water.

The Final Word

Everywhere you look you will see a recommendation to store bleach for water purification. I have made that recommendation and so have many, if not most, of my blogging peers. What you may not have seen is that liquid bleach has a limited shelf life of 6 to 12 months. I fear that this could be leaving a lot of people ill-prepared to produce safe, potable water in an emergency.

This means that a person that began prepping a year ago, and does not know to rotate their bleach, is already living with false security when it comes to water purification. And what about people that have been prepping longer?

As long as pool shock is stored properly, it will have an almost indefinite shelf life plus, a small one-pound package will treat many thousands of gallons of water. Ten thousand to be exact. It can be mixed and used as potable water and as a disinfectant, just like bottled liquid bleach. So if you have a water storage tank and need something for emergency water disinfection, a hypochlorite solution could work out well for you.

At the end of the day, do your own research and decide for yourself.

Enjoy your next adventure through common sense and thoughtful preparation!

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88 Responses to “How to Use Pool Shock to Purify Water”

  1. Thank you Gaye for getting a bunch of tangled up instructions straightened out! I will be writing these out, and probably be giving them a test run. One question, can the “stock” be used in the laundry room in place of normal liquid bleach or does it require more dilution?

    • I left out the part about use in the laundry because once again, I read conflicting information. What I do know is that cup per cup, the pool shock stock solution is much weaker than liquid bleach so logically, the quantity needed for a load of laundry would be huge if used in liquid form.

      I do like Ken’s use of powdered calcium hypochlorite in the laundry though. That would be so much easier and safer to use than the liquid and would eliminate the fear of dripping the liquid on surrounding carpets. (My washer is in a small closet not a traditional utility room.)

      I plan to get a test kit so I can measure the effectiveness of my pre-made stock solution over time. Does it become useless in a year? That would be good to know although my intended use would make it up fresh as needed.

      The list of questions goes on so keep them coming. I plan to do some additional research.

    • Why not just buy a Big Burkey and some extra filters. Check with MFG, TO SEE IF THEY CAN BE SANTIZED WITH BLEACH or what ever and you can use water from creeks or rivers, farm ponds if not used to water cattle.

    • I do have a degree in chemistry and worked for a large swimming pool distributor. If you use Cal Hypo there is one VERY IMPORTANT thing to know (there are a few others too). It is an OXIDIZER!!! That is, it produces it own oxygen for combustion. You could put it in a vacuum and ignite it and it would still burn. You can’t put it out with a fire extinguisher or even 20 of them. Watched my warehouse guys handle some wrong one time and they went through 20+ extinguishers fast.
      It reacts (ignites) with organic material (cigarettes, oil just about anything in your trash can) If you have to dispose of it dissolve it in water and pour the water in the toilet. Be careful with this product. It’s safe if you use it properly. It does not have a long shelf life 12-16 mos. tops. In St.Pete Fl a large distributor’s WH burnt to the ground because they miss-handled it.

  2. I use undiluted colloidal silver to purify water. No odor, it works, it’s easy…just pour some in, and it’s good for us. Spraying and letting it set on counters, etc. for 10 min. disinfects them. Spraying it on food makes it last longer. Drinking it keeps us healthy…very inexpensive if you make your own. There are dozens of uses for it and it’s always SAFE.

    • Using colloidal silver is on my bucket list of projects. Like the use of calcium hypochlorite (pool shock), some of the instructions and dilutions I read make my head spin. I want to break it down into simpler terms.

      I know you have sent me information in the past; I need to dig it out and read it again. If I need some help, I will let you know.

    • Gaye, when you go to make CS you may want to get a TDS meter, if you don’t already have one. Amazon has one for around $10.
      (TDS = Total Dissolved Solids) – it does not say what the solids are, but if you start with distilled water it reads 00.0, so any reading on the meter would be what you put in it (silver for colloidal silver). Reading is generally in parts per million.

      under 50 ppm – ideal drinking water
      approximately 350 ppm – average tap water in America (mine shows 34 ppm)
      If TDS levels exceed 1000 ppm, however, it is generally considered harmful to human health and should not be consumed.
      (data from

      This should also help checking how well your drinking water filter is working.

  3. Also, colloidal silver (CS) can be used in the washer to disinfect and clean clothes. I wash my hair with it and it keeps it clean much longer than normal. I can’t think of anything CS can’t improve.

  4. We all needed to know this Gaye. Thanks. I’m like JimW. How does your stock solution compare in strenth to my bottled bleach? For long term water storage, I have always poured liquid bleach into my storage container, swished it all around, then poured it out. I then added my water. This is suppose to add the correct amount of bleach to your container to hold down nasties while in storage. Could your stock solution be used in the same way?

    • Why not simply add some pool shock solution and store it that way? That would be easy enough and a no-brainer. Basically, you would be using the pool shock as a bit of insurance against nasties that may (or may not) develop while the water is in storage.

      For example, I used an Aquimira purification liquid when I filled my 55 gallon water barrels. I could have used the calcium hypochlorite stock solution instead. The math? 55 gallons/100 = .55 gallons of pool shock. It could be done.

      For me, the most important aspect of this article was figuring out the math so that I could create drinkable water on the fly. That plus, as always, skill building via practice.

    • Pool Shock when mixed with water lasts no longer than bleach in a bottle.
      I plan to mix only what I need in a 2 liter bottle with the directions below.

    • As a chemist, JayJay is right. You showed storing the stock solution and it will get progressively weaker over time. After mixing the stock solution with your water to be purified, Immediately after adding the stock solution, smell the water and make sure you can smell chlorine in it. You have to let it sit for 20-30 minutes for the chlorine to kill any target micro-organisms, then it is safe to drink. Just pour the water back and forth between two containers to remove any residual chlorine smell/taste. (It is displaced by air as it is poured.) Thank you for a very well thought out and through show and tell.

  5. Thank you so much gaye.. You know we have used this for years as a laundry bleach ( one tablespoon per load) and have heard that is could be used to disinfect water but every time I read something new the amounts used was different.

  6. Thank you Gaye for the point blank article with the bits of humor in it. I too have found so many articles that are all over the place and not to clear or conclusive with their information. A couple of suggestions. You should wear a face mask while mixing this chemical and outside is best; avoid making in damp conditions. Also there should be a waiting time between treating the water and drinking it.(I know you know this but the article didn’t state this)
    Question: Once the water has been purified and some time has passed like 20 min. does the bleach in the water become inert?
    This article I read // is one that is all over the place, it is the responders that have some good information (and some bad information) that I found informative. One gentleman gave the information on the ‘other additives’
    ‘OTHER’ ingrediants in calciumhypochlorite, ‘pool shock’. As with any list of ingrediants(food or food) the first ingrediant is your largest amount. So here goes.
    First is chlorine; your active ingrediant 47>76%. Next is your OTHER ingrediants; sodium chloride (plan salt) 10>20%; cal.chlorate 0>5%; cal.chloride 0>5% (used in beer brewing, flavering pickles, A firming agent for turning soybean curd into tofu——). cal.hydroxide 0>4%; (also called slaked or pickling lime). cal.carbonate 0>4% (think of Tums/antacids).
    One last thing.Check Ph after treating. needs to be 7.2>7.6
    Another not so gentlemanly “Mark” gave a response to Christopher’s information. But “Mark” had sound advise on the dangers of storing calcium hypochlorite. (People need to be nice in responding to people’s lack of knowledge or ignorance)

    • I am not sure you would call it inert, the Chlorine vapors off. The Chloring doesn’t want to stay in the water and will convert to a free gas if given the opportunity. Similar to CO2 in soda.

  7. Just wondering if you ran the water you purified through your Berkey water system and if there would be a reason not to do that. I would assume that it would improve the taste, but not that familiar with the Berkey products to know if the water you purified with the Pool Shock would some how contaminate it.

    • I had wondered the same thing as I was writing the part about “not as sweet tasting” as the Berkey. I don’t see why not, though, since all we are doing is creating chlorinated water. Naturally, we do not want to ruin our Berkey filters so I do plan on getting a definitive answer.

    • I have a shelf lined with ‘instants’–Tang, tea, fruit drinks, Country Time, even Koolaid!!!—lots of these to kill the bleach taste if there is one.
      Good luck and God bless.

    • I treat my cistern on a regular basis with the pool shock. I run the drinking water through the Berkey and the water is wonderful. It tastes like spring water.

      It is always an estimate how much shock to use. It depends on what is in the water, mud, leaves, larvae etc. (I also have pool.) You want to smell strong chlorine after treating the water. The smell will dissipate.

      Buy a pool test kit that has chlorine, PH and alkalinity testing. When you finish treating with shock, you want the reading to be off the chart with the chlorine and let it come down on its own.

    • The politest kit is good to establish a base line but when the pool test kit shelf life runs out you will always have your nose to determine if it is enough. The reason they call it pool shock is that you must out enough in to kill all – which is a shock to that system.

      It is great that someone is using pool shock in a way I could only project to using it after the SHTF.


  8. Thanks for the helpful information…Any guidelines for using this as a “wipe-down” disinfectant? BB

  9. I have a 30,000 gal swimming pool. I have always thought of this as my water back up plan. I keep 30 days worth of bottled water on hand. Collect rain water off my roof. Does anyone know the best way to change swimming pool water into drinking water? The pool water has chlorine, acid and clarifiers in it. Just my luck I would probably need the water just after I’ve shocked the pool.

    • I am checking into this for you. The last thing I want to do is pass on bad information. Of course, eventually the chlorine would dissipate on its own, but still…

      I am pretty sure the SolarBag from Puralytics will work although it does seem counter-intuitive. //

    • I would recommend NOT using pool water for long term drinking purposes. Many of the chemicals such as algecides used to keep the water clear are not safe for general human consumption. Nothing short of distilling the water will remove those chemicals.

      In addition, sunlight denatures the chlorine. Even covered with a tarp, within a week your pool’s chlorine levels will be at 0. And while you might have spare chlorine on hand to continue to mix, if you have no electric power to run the pumps, filtration, and agitation then its effectiveness will be diminished because it is not dispersed adequately throughout the pool.

      And finally, studies by the CDC indicate that over half the pools in Atlanta contain E coli. Although the study was conducted in Atlanta, there is no reason to believe that the study would not be consistent throughout the US. //

      In essence, within just a short time, water within pools could and should be considered questionable. The risks skyrocket if it is not a pool that you personally treated. So if your pool is your long term water solution, think again.

  10. So the pool shock is granular. Instead of formulas how to mix up basically a bottle of chlorine, would you be able to convert to say 10 granuals of pool shock per 16 oz glass of water so you don’t have to make up a large quantity to carry around? It would be great to just dump a certain number of granuals straight into your drinking container. The question is, how many granuals per ounce?

    • Pool Shock is a powerful and potentially toxic chemical if not used properly. Also, it is powder-like and would be difficult to measure on a grain by grain basis.

  11. Is there a particular reason that you mix up the solution first, and then purify water using the solution? Why not use the pool shock (in the proper quantity) to purify the water directly?

    • To give you an idea of its strength, 1 pound treats 10,000 gallons of water. Breaking down the measurements would be unwieldy. Plus, as I mentioned above, Pool Shock is a powerful and potentially toxic chemical if not used properly. It is much safe when used in its diluted form.

  12. “Make sure that Calcium Hypochlorite is the only active ingredient in the product and at 65% or greater, (Note: You will not be able to find this concentration at Wally-World, you will need to go to a pool supply store) with no added anti-fungal’s, or clarifiers, if not you can seriously endanger you and your family.” Quote from article below.
    Here is an article that also looks at the 1:100 ratio and how to purify small amounts of water. //

  13. I would also suggest that this should be added to everyone’s barter supply list or your gift packages you plan to give away.

  14. Please be sure to always add CHC into water…..never put the CHC in the container first adding water to it in a small container can have a volatile reaction.
    And for the record, the more bacteria in the water, the faster the chlorine is used up. Sunlight also uses up the chlorine faster…that is why the recommend shocking at night.

    • Hi Joanne, I agree. As Gaye said: “Be sure to pour your pool shock into your water and not the other way around.”

      The reason: Putting pool shock (or any other chemical) into water creates a diluted solution which slowly becomes more powerful as you add more. Depending on the chemical, the reaction may create heat, and you do not want to inadvertently create a great deal of heat.

      Adding water to the chemical creates an extremely concentrated solution, may create a great deal of heat, and can result in an explosion which throws hot, toxic, highly alkaline or acid chemicals all over, including on you.

      So, the simple way to be safe: add chemical to water, not the other way around.

    • Exactly, treat the 2 liter of water like a pool.
      One always throws the powder into the pool water; likewise, the CH is put into the 2 liter.

  15. Hi, Gaye,
    I’ve really been enjoying your posts…I’ve gotten more useful practical real life-type information from them than from any of the many prepper sites I’ve been lurking about on. It’s appreciated!
    As a prior-military father and husband, I’ve been prepping since the early ’90’s in order to be prepared for whatever nature (and our government) has in store for us…in that vein I’ve found a great appreciation for the common-sense practicality ideas like pool shock water purification.
    I’d like to formally request you do some experiments with the colloidal silver and enlighten us all on its properties as soon as possible.
    Thanks again for all of your work and the sacrifice that goes along with any blog.

  16. Great information even if I can’t use it. Too many around me with allergies to chlorine. I too, use silver but never tried the colloidal silver so will investigate.
    I’m told I’m teasing the local lab since I bring in water samples frequently. Why? I’m testing how to purify with just what might be at hand if/when someone desires what I have more than do. 😉 I’m preparing for that too….better to walk away living than the alternative. 😉

  17. As an ex water plant operator for 37 years and a everyday user of CS that I make myself, I’d like to make a comment. While I use CS for many things and own and read several books on the subject, I’m not sure if I would count on it for water purification. The main point that I have is this. If you use a generator to make your CS with, as most people do, your average dose in PPM comes in from 10 to 17 PPM. Most people use the 10 PPM as their everyday strength. I usually make a 10 and a 17 batch. I use the 17 for external things and the 10 for internal. A generator will make a higher dose but at a higher dose you will get silver starting to coagulate in the water which must be removed and you will use way more power and time to do this. You will also have to keep pulling the rods out and clean them so much that it’s just not worth the effort. When you may see CS for sell that says it is hundreds of PPM it has be made with a silver salt and is not true CS. My point on water is this…if you have a batch of 17 PPM and you want to treat a gallon of water, how much would you need to add? How long would it need to rest before it was ready? I have never seen a formula for this in any of my books. While I do not believe that it would hurt anything to add it to your water. I don’t think that I would feel safe using only that method. If anyone knows the formula, I would welcome this info.

  18. You stated you were not a chemist. I am, and I’m a nutritionist.

    Pool shock is ok for 1 glass. The ‘other ingredients’ will kill a compromised person in 1 day or a normal person in 3 days. Pool shock requires stabilizers and bacterostatics and because this is not a food item, they are not required to tell you they are in there. It states right on the package to not drink the pool water or use for water purification. The active chemicals are not stable, not pure, and certainly not for ingestion.

    If you actually use your head, there is a great reason why liquid bleach and Ca(OCl)2 are not used by public water sources: they are toxic. It is the reason why the more expensive Cl2 gas is used or NaOCl is used.

    • Hi Chris, I am confused.

      You said “there is a great reason why liquid bleach and Ca(OCl)2 are not used by public water sources: they are toxic.”

      My understanding is that chlorine bleach works precisely because it is toxic, as are the others. If they weren’t toxic, they wouldn’t kill bacteria or viruses. My understanding is that C12 gas is used because, for the quantities a municipal water system handles, while dangerous to handle, it works very well and is cheaper. Bleach isn’t cost effective in those quantities.

      I did some research a while back on using bleach, (Clorox specifically) for sterilizing water in an emergency. The American Red Cross “Food and Water in an Emergency” page recommends it. Their page:


      Scroll down to their pages 11-12 for using bleach.

      The site recommends bleach for storing water: // Clik on the Water Treatment tab for using bleach to treat suspect water*.

      While I am not personally familiar with the reliability of the Family Survival Planning page, it has warnings about using iodine, along with bleach instructions: //

      The Clorox company’s disaster page for purifying water:


      All of the professional opinions I can find say that fresh bleach works just fine, and that since bleach breaks down, fresh bleach is stronger than older bleach. Year old bleach isn’t worthless for purifying water, but you have to use more.

      None of this addresses the issue of using pool shock to treat water. I would like to see a statement from a manufacturer about safety. They may be highly reluctant to state that it is safe, even if it is, if it is not a registered disinfectant for drinking water. Your comment about their not being required to state other ingredients because it is not a food item should raise a big warning flag for all of us: I would want to know what is in it. Until I know I will continue to rely on bleach, buying some fresh whenever we have a hurricane warning.

      My understanding, which may be both flawed and dangerous, is that while a filter like an AquaStraw or AquaStraw Family size will filter out bacteria, cysts, and viruses, it will not filter out dissolved chemicals. For that one needs a purifier like an AquaPail. We have all three in our hurricane supplies.

      It seems to me that the best water is the water which one has stored before an emergency occurs. After that, I prefer sterilizing with bleach. Down the list comes swimming pool water which I would run thru a filter and, ideally, a purifier.

      * Of course, the “Managing Water” page also says “Do not drink carbonated beverages instead of drinking water.

      Carbonated beverages do not meet drinking-water requirements. Caffeinated drinks and alcohol dehydrate the body, which increases the need for drinking water.”

      To my mind, that is dangerous misinformation: While caffein does increase urination, drinking a caffeinated beverage will, net, act to rehydrate you. It just won’t rehydrate you quite as much as plain water would. If one has the choice of drinking caffeinated drinks or not drinking, one is FAR better off drinking.

      I bummed around North Africa, the Middle East, and Central Asia during the 1970s, and I guarantee that the Arabs, Persians, Afghans, and Pakistanis do not drink plain water: They drink tea and coffee. In areas like Jordan in the summer, where IIRC the UN recommends drinking 17 liters of water per day, the Arabs drink hot caffeinated beverages. Part of that is because brewing coffee and tea require boiling the water, which sterilizes it. Hot drinks also make one sweat, which in turn cools one off.

      As for drinking suspect water without treating it: If your choice is drinking it or dieing, drink it. I took a train from Kerman, Iran, to Quetta, Pakistan during the summer. The train people apparently didn’t warn passengers that they must carry sufficient water themselves. While many did, a great many, including I, did not. We didn’t know.

      It was three summer days and nights through the worst desert I have ever seen, sand as far as one could see, the train stopping while crew shoveled sand off the tracks, and there were knife fights over water. Ditch water, dumped in the ditch by the train to supply a small group of houses. People didn’t know how long the train would stop, they didn’t know how much time they had to fill bottles from the ditch, so they pulled knives and used them so they could get to the ditch water.

      Pakistanis drank it, I drank it, and I later came down with infectious hepatitis, which is no small thing. Unless I had drunk that water, though, I would not have lived long enough to get hepatitis.

    • Penrod – when it comes down to doing it or not staying alive most people will do the things that they said “NEVER” to.
      However, I personally think I would not have survived as a member of the Donner party!

  19. This site has instructions for using pool test strips to evaluate the strength of your solution. Should make the process a lot more precise and predictable.


  20. I have simplified if anyone needs this:
    1 to 2, then 2 to 1
    1 teaspoon CH to a 2 liter bottle to make the solution
    Then 2 teaspoons of the solution to 1 Gallon jug of dirty water.
    1 to 2, then 2 to 1

    Easy to remember.

    I keep a teaspoon measurer, a gallon jug, and a 2 liter bottle in a canvas bag with my pool shock.

    • Thank you so much for this. I don’t know what I was missing in the directions but I seemed to continuously miss something. Oh, but even I get the 1 to 2 and then 2 to 1 thing. 🙂 Thank you!!!!

  21. Penrod…
    1) bleach has a 3-6 month shelf life
    2) CH has an indefinite shelf life if kept cool and dry
    3) bleach requires lots of space to store
    4) CH on a shelf doesn’t take a lot of space

    • Hi JayJay, all true, but we prep primarily for relatively short term aftermaths of problems like hurricanes, and to a lesser likelihood, earthquakes. It would be extraordinarily unusual to be unable to buy fresh bleach a couple months after the initial event. We also use bleach around the house, so it is pretty unusual to have bleach more than six months old even if there was no warning of the event. In that case, Clorox Company says to just use more bleach- until you can still smell some in the water after letting it sit for 20 minutes.

      We also store about 2 months worth of water at all times, precisely because earthquakes don’t give warning. With a little warning we can store another 20 days’ worth in containers we normally keep empty.

      It is at least possible that that would be insufficient, but we think it unlikely that water would not be available by the time we used it all. In that case, though, we would fall back on the LifeStraws and AquaPails and whatever water was available.

    • Most throw away plastics like Simply Orange and Simply Grapefruit.
      Yes, they are plastics, but I don’t keep them setting in the sun. They are in a cool room with the curtains doubled and an insulated one at that.
      I do have a Berkey to filter any nasties in those plastics.
      Water stored in plastics is better than no water in my thinking.
      700 gallons in the garage in blue food grade 30 gallon drums.

  22. Good article and the powder is much better than the liquid or the tablets(hard to use.) If you want to be very certain about the safety of your end product you can order a Hach free chlorine test kit. They are easy to use and it will tell you how many parts per million free(not used to kill bacteria or viruses) remains in your end product. It should be no more than 2 parts per million and there should be some residual or you can’t be certain you have killed all the bugs.

  23. Great article on using pool shock to purify water. Now I’ll tell you how to get the chlorine out for drinking. Use vitamin C. That’s right. I first heard about this from the San Fransisco Water department.
    Here’s a link.

    I used this for my plants. I can’t remember the exact amount I worked out so I know this will drive you crazy but a good/heavy pinch between your thumb and finger into five gallons of water was about the amount. If you want to make sure use two pinches and that’s more than enough. You can test this and see it works. Add the pinch to a white five gallon bucket and stir vigorously in a circular manner. Let sit for 15 minutes or so and you will see a little grain in the bottom center of the bucket. That’s the chlorine bound with the vitamin C. You pour off the top to drink and discard the grain in the bottom. You do have to drink the water soon or it will get algae in it. If you search “use ascorbic acid to remove chlorine pdf” you will get a lot of links for this procedure. Also you’ll get the exact amounts if you’re using the method on large amounts of water.

    • That is terrific information. I printed out the document and when I have a chance, I am going to try this. Time for another show and tell?? Thx.

  24. `I haven’t read all the comments, so I apologize if somebody addressed this already. I appreciated all your safety tips for the handling of Pool Shock, BUT there is a picture of you smelling the bottle for the chlorine smell. Your face is too close to the jug. Do NOT stick your nose down to smell potentially toxic solutions. Leave your face above the container and use your hand to waft the smell up to your nose- wave it from the container mouth up to your nose. It works and it protects the nasal mucosa. Thanks for the work you did on this.

    • Shannon – You are the first to mention this so I do appreciate the feedback. When I have time, I am going to update the article to include this information. I can’t thank you enough.

      — Gaye

  25. One last comment- no one has ever consumed pool shock treated water long term—or this is what I read.
    So, if bleach treated water is NOT great for little tummies, what about CH treated water for little tummies??
    It would be appreciated if this issue was addressed.
    Would it help to use the Berkey AFTER our contaminated water is purified??

  26. When storing water in 55 gallon drums, why go through the process of creating an intermediary concentrated solution that will go bad over time. Wouldn’t it be far easier to simply add x tsp to the barrel as it is being filled?

  27. Your a lovely lady and your efforts are precious.
    I do you hope you have a significant other as in the event of true catastrophe I’m quite sure you would perish in round one.
    When people are so hungry and thirsty they will kill you to take yours a six month stockpile of water is ludicrous. You can’t easily fetch more than a gallon. I don’t carry but half that.
    Please study the injuns a bit. Dirt is the best survival cleaner you can get. Bathe in it and clean your mess kit with it. Pee I the woods and poop near your bunk.
    FYI you can get more detailed units of measure to make shock useful. We had all be consuming it all our lives. The restaurant industry labels it potato white. Its in everything that air disclosures, whilst etc. PS restraunts don’t wash veggies. They get a soak in potatoe white and water and served. Bon apitit and travel light. You can carry more bullets like that.

    • These are very powerful and highly concentrated chemicals. Until the Pool Shock is diluted, you will want to protect yourself. This is no different than working with chemicals in a lab.

      Once diluted, however, it is safe to drink in the same manner that water with a few drops of chlorine bleach added in safe.

  28. Hi. Thank you for all of the great information, and I hope this doesn’t make your head hurt! I have probably visited 30-40 different websites regarding Calcium Hypochlorite (a mix of both government and personally maintained sites) and I would like to try and have something cleared up, because the information on this site, as well as the EPA’s own site is conflicting with most of the other sites.

    First, my purpose in analyzing Calcium Hypochlorite [Ca(ClO)2] is in its long-term stability as a water purifying agent. I try to be practical in my preparedness wherever possible, so for bugging out I want to base my water needs on the most common container in the world, the everyday 16.9 fl oz (500 mL) plastic water bottle. They are easy to carry, find and scavenge. Based on that, I ran some very quick calculations on high-test Calcium Hypochlorite (anything over 65% chlorine content, with the remainder being inert elements) and came up with the following…

    Using the commonly referenced guideline of 7 grams of Ca(ClO)2 per 2 gallons of water to create a 5-6% Chlorine Bleach Solution @ 500PPM, would mean that you only need 3.5 grams per gallon. There are 7.57 16.9 fl oz (500 mL) water bottles in a single gallon, so dividing 3.5 grams by 7.57 bottles yields .46 grams of Ca(ClO)2 to make a single 16.9 fl oz (500 mL) bottle of Chlorine Bleach Solution. I will just round this to 0.5 grams. My intent for my various go-bags (at home and in our cars) is to keep 2 small glass vials, each with .5 grams of pre-measured HTH Ca(ClO)2 in them, then each stored in sealed bags. They only take up about as much space as a pair of dice! That way if I am ever in a situation where I need to purify water or apply a disinfecting agent, it will be as simple as pouring the contents of one vial into a single water bottle. No thinking, no measuring required.

    Now for the confusing part. Just about every site out there (including the CDC, the WHO, FEMA,, and even the EPA) lists treating water based on the following…
    Using a stock of fresh 5-6% Hypochlorite Bleach @ 500PPM (or 500 mg/L), treating 1 Gallon of water:
    >> EPA (Normal Water) – 8 Drops [NOTE: this is a SIGNIFICANLTY different guideline than the 1:100 ratio that they use in their ‘general statement, see below]
    >> EPA (Questionable Water – Murky or Very Cold) – 16 Drops
    >> CDC Worst Case (Unknown Water, Unknown Bleach) – 40 Drops

    Several technical reports have even come out lately in Medical Journals that state even the 8 Drop guideline is too high (it should be closer to 4 or 5), that using 1PPM is all that is required over 45minutes to kill off any applicable foreign agents, everything else is just a waste. The studies were done in light of the weight associated with carrying bleach to remote African villages, so they were trying to be as precise as possible.

    I like using the 16 Drops / Gallon guideline, as this will help to account for the rapid deterioration of the bleach solution over the first 30 days (at which point it somewhat stabilizes), and the fact that I am using a clear water bottle instead of an opaque brown container, like the CDC recommends to inhibit deterioration. So, based on the 16 Drops, that would mean 2 Drops per 16.9 fl oz (500 mL) bottle of questionable water. “Drops” are certainly not a precise way to measure, but they are close enough, and can be defined as follows:
    >> 1 Teaspoon = 5 mL = 80 Drops [Google conversions lists it at 100 Drops]
    >> 1 fl oz = roughly 30 mL = 6 teaspoons = 480 Drops [Google conversions lists it at ~600 Drops]

    This article, and even the EPA guideline referenced at the very top of the article uses a 1:100 ratio for [chlorine solution] : [questionable water]. So, 1 Pint (or 16 fl oz) to 12.5 Gallons (or 1600 fl oz) to be exact, which is dead-on with the 1:100 ratio. Based on the fact that 1 Gallon contains 128 fl oz, that would mean you need to mix 1.28 fl oz of chlorine solution per gallon of water to be treated. This equates to approximately 38 mL, or nearly 8 teaspoons, or even 600 Drops as calculated above. If you use any of the online ‘drop conversion calculators’ online, it puts 1.28 fl oz in the 700-800 ballpark.

    So, to treat a gallon of water with a 5-6% Hypochlorite Bleach @ 500PPM, am I using 8-16 Drops, or 700-800 Drops? These guidelines are differing by nearly a factor of 100! If it were a factor of 2x or even 5x, I wouldn’t care, but these differences are significant. The person that I bought my 68% HTH Ca(ClO)2 actually provided guidelines imprinted on the sealed containers that use 5.5 grams per gallon to create a nearly 1,000 PPM solution and then states to use 1.5 fl oz of the stock chlorine to treat 1 gallon of water, which would result in a chlorine solution that is also significantly higher (almost double) to that of the EPA guidelines. And yes, the EPA completely contradicts itself by using the 1:100 ratio, and the 8 Drops per gallon, even on the same website. I have seen articles that say too high of a chlorine PPM will cause illness and diarrhea, but I have also seen articles that state this is entirely false, you won’t have any issues until you go to a much higher ratio, in fact it would be so unpalatable that you would recognize the high content right away.

    In summary, this is very confusing  but I will stick to the 16 Drops / Gallon guideline, for now. So, I will let the water settle and strain it first (if necessary), add 2-3 drops per 16.9 fl oz (500 mL) bottle of questionable water to be safe, let it sit for 30 min, then repeat if it doesn’t have a slight chlorine smell. If I were using the 1:100 guideline, I would be adding 80-100 drops or 5 mL (because a 16.9 fl oz is also precisely 500 mL), but that seems entirely wrong. Anyone with a kid that has used a 5 mL syringe dispenser for cough medicine knows how much 5 mL is, and that’s waaaaay too much to use to disinfect a single a single everyday plastic bottle of water. My conclusion is that the 1:100 ratio is simply wrong. Very wrong.

    Or, I must be missing something very simple, any feedback is greatly appreciated! Some of this has to do with the theory of small numbers when dealing with guidelines based on large numbers, but to be off by this much is concerning.


    • Not purifying contaminated water will kill you a lot faster than any damage lightly chlorinated water might do, and as others have pointed out just the act of pouring the water between two containers and aerating it will reduce the chlorine levels.

      Check out // for a truly frightening list of diseases found in untreated water supplies….

  29. Hi. Do you know what the other 32% is, that is not the Calcium Hypochlorite that is referred to on the label as “other ingredients”?

  30. They are “inert” ingredients that do not create a chemical reaction; mostly fillers. As far as the exact composition, in my own research I was told that they can vary from one brand to another but that they are harmless.

  31. When you ingest Calcium Hypochlorite (MMS2), it’s activated by stomach acid and produces hypochlorous acid which is a potent germ killer, normally found in the body. It does not release “chlorine” as some internet disinformation peddlers have falsely claimed. google,calcium hypochlorite mms 2

  32. I am a licensed clinical laboratory scientist and just wanted to add a little info. One should not be entirely dependent on the EPA guidelines for solution strength. The solution strength needed to kill viruses and organisms is dependent on a number of factors. The cleanliness of how the water looks and smells before it is treated is probably the most important consideration. Of course drinking too much chlorine, is also unacceptable. Decontaminate the cleanest water available and be sure to first let it sit with good mixing for at least 20 minutes before drinking. Also, decontaminated water has a shelf life. I would not prepare more than a weeks worth at a time.

  33. Great article, as usual. One note for your, and everyones safety: chemicals should not be smelled in the way you pictured. Proper technique starts with wafting (using your hand to wave some of the smell toward your nose), if the smell is mild you may then move in for a stronger sniff. However, if you start by smelling as pictured, and the chemical is strong you can get hurt (or in some cases killed). Safety first.

  34. Why not ten drops bleach: Clorox/Purex to one gal. of water from mountain stream,river or creek.

    Would this not purify it?

    Just wondering in TN.

    • The problem with bleach is that it has a limited shelf life of six months to a year. Undiluted pool shock will pretty much last forever plus a tiny bit goes a long way.

  35. 02Jan.2016

    If we experience an EMP attack, (Electronic Magnetic Pulse) where a Nuke is set off in the upper levels of the sky 10 to 20 miles up in the wild blue yonder, all the lights will go out and they will stay out for several years. The electronic in all the newer vehicles will be fried like in Sunny side Up is the way I like my eggs if you get my drift, if you don’t it means it won’t work ever again! All the electronics in the Auto Parts Stores will be fried too! The only thing that will run is a vehicle that uses the old points where you have to set the gap with a feeler gauge. Most people & a lot of the younger mechanics don’t know how to install or set the point gap in these older type vehicles, be they land or water type vehicles. Boats Air boats etc.
    Well thats all folks.

    I JUST PRAY The Rapture takes place first. I sure don’t want to have to deal with this type event. I am too old & crippled up to handle anything like that.

    Highly recommend you all, that is Hillbilly talk meaning all of you/everybody or every one get and read Ted Koppel’s book: Lights Out – Cyber Attack.

    Best Wishes to you all.

    MN1 Robert Briggs, USN Retired in Tennessee.

    The Best Thing any of us can do is call your Congressman/woman or Senator and DEMAND THEY START IMPEACHMENT PROCESS AGAINST THE idiot in the White House ASAP!
    MN1 Robert Briggs Vietnam Vet & 20 year USN Retiree.

    You can order it from Amazon, mine is due to arrive on 04Jan.2016.

    • I haven’t read ted Koppel’s book (Lights Out – Cyber Attack). I will put it on my list. I have read, One Second After by John Matherson. It is a novel but very thought provoking.

  36. Hi everyone. My husband and I are new to prepping. We bought 3.5 gal. “Water Bricks” to stock up on some water. We’ve been filling them with distilled water from the store. My questions are: 1. Do we have to rotate these once filled? (is there and expiration on them?) 2. Do we have to use a water purification form when we use them or as we fill them with the distilled water? Please help.

  37. We live on a property that has a 500 gallon, galvanized water storage tank. Is there any issue with using the pool shock with this tank?

    • I’ve read on other sites that you don’t want to mix this together in a metal container. Acid resistant plastic only. You can reuse your old bleach bottles for example.

  38. Don’t sniff directly from the jug! You can burn your nose that way.
    In high school chemistry they showed to waft your hand across the opening toward your nose and sniff carefully.

  39. The issue of CH (Pure pool shock) as a water purifier has been kicked around for some time. Few thought I want to share with all:
    Longterm storage of CH is a challenge. The manufacture recommendations is cool, dark (out of any direct light) and well ventilated. Cool and dark is the basement but never truly ventilated? The storage of CH crystals is of concern because the CH decomposes to Chlorine gas. This is not nice stuff. I tried to put in in a kerr canning jar and in 6 mo to a year the metal ring was rusting on the outside. Cl gas is aggressive to most materials including plastic. I suggest you check your plastic lid and see if it hasn’t gotten quite brittle? And past article talked of an apartment deweling individual with limited storage space put can good and CH in the same confined closet and found all his cans quite rusty and the cardboard box falling apart. Storage of the crystals needs to be better thought through. I don’t have the answer.
    Use the cleanest / filtered water you can get. I have read that CH will kill girdia but was questionable about the dormant pods but they are larger than the critter.
    Also, when you start worrying about the bulk solution or the water being purified relax. Did you have to take swimming lessons at an indoor pool as a kid? Ever have an early lesson? Smell the chlorine in the pool room? That was most likely on the high side but since you are reading this not fatal. Add your CH solution to your to be drinking water, mix shake well, leave set for as long as you can, 30 to 40 min and then smell it. If you don’t smell the pool smell add more solution and do it again. If you do smell the pool smell begin to vent it off by pouring from on container to another and then drink. The pool chemistry test kit is a good idea but all the reagents in it have a shelf life. I am a lazy prepper. That is why I like CH, small volume, long shelf life, simple testing – your nose.

    • Addition to above:
      I spoke to a chemist at a plant that makes CH (Pool shock) and his comment was that the manufacturing process consists of converting Chlorine from various salts to CH. The inert portion is the original salts. To get higher percentages of CH cost more than it is worth so they stop the process at an economical level, it gets the pool shock job done but isn’t crazy expensive. He did not have a suggestion for long term storage. They sell it in plastic bags that are not gas tight for Chlorine gas. The stores that store / sell volumes of CH have better than average ventilation.

  40. Has anyone offered an acceptable means of storing CH for the long term. I have put the plastic bags of CH into repurposed vitamin bottles of the proper grade plastic and put these bottles into a 5 gal plastic bucket with the best selling lid I have and this is stored in the garage. The garage gets warmer than I would like but it is the only storage spot in my house that has any real ventilation.
    To me the prepper movement has two categories, the first month and the first two years. A recent bought bleach bottle will cover the near term but long term water purification would be another issue. And, like I have said in the last I am a lazy prepper, I hate to rotate stock and love 5 gal buckets of properly stored wheat.
    I would love to hear other peoples ideas on how they have stored HCH.

  41. Why oh! why can I not print this? I did a Ctrl-P and got 2 pages and nothing in those 2 pages.

  42. Thanks for the info, especially the ratios. With this Wuhan virus, I’m spending the weekend taking stock and updating my preps. I wrote exactly what you wrote on my bucket that I’m storing the shock in. If this thing were to get serious, and water becomes an issue because of a quarantine, and no power etc, my plan is to treat all water we use with the pool shock solution, and from that, any water that is consumed, to run through our Berkey.

  43. Thanks for the vote of confidence but I still have the insecurity with how long the Pool shock will last. The pool shock is in a constant state of moving to the lowest free energy (degenerating) which is why I was so concerned about finding the correct plastic to hold it in a cool, ventilated environment. But that doesn’t answer the bigger question, is Chlorine and the filter capability of a Berkeley up to the challenge of stopping a virus. Viruses are very small and until infecting an organism, not really alive??????? Can Chlorine kill an inactive virus?

  44. Can pool shock be used as a disinfectant and sanitizer to kill covid-19 virus? The CDC says that a 1:10 solution of regular Clorox bleach will do the trick. Can a solution made from pool shock do the same? I note that pool shock is calcium hypochlorite and Clorox is sodium hypochlorite (from the Clorox website). What difference calcium vs. sodium for this purpose?

    • You have to do the calculation, how much chlorine in the pool shock (between ~30 & 50%) and how much chlorine in the bleach being referenced? Don’t lose site of the fact that depending on your source, bleach degenerates (loses it’s chlorine) up to 50% in 6 months. Memory gives me a 5% for fresh bleach. Most recipes for pool shock end up with a volume (5 gal) of bleach that is then used as bleach.

      If you have 5% in bleach and they say a 1:10 dilution will disinfect for the virus why do you need a 90% alcohol for homemade hand sanitizer?

  45. History Note: a long time ago in Europe they drank ale and wine because they knew that the water would make them sick(it was always dirty}…// while building the railroad across the United States, the Chinese were much more productive than the Irish because they drank tea made with boiled water whereas the Irish drank the{dirty} water and used liquor alot and were therefore sick alot…// we actually CAN learn from history even if we are somehow doomed to repeat it………

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